The spectral parameters of Nd^3＋ ions in Nd^3＋-doped NaGd（MoO4）2 crystal have been investigated based on Judd-Ofelt theory and obtained as follows： The intensity parameters Ωeff are Ω2 = 24.77×10^20, Ω4 =...The spectral parameters of Nd^3＋ ions in Nd^3＋-doped NaGd（MoO4）2 crystal have been investigated based on Judd-Ofelt theory and obtained as follows： The intensity parameters Ωeff are Ω2 = 24.77×10^20, Ω4 = 7.31×10^-20 and Ω6 = 6.91×10^-20 cm^2. The radiative lifetime is 100 μs, and the quantum efficiency is 93.9%. The fluorescence branch ratios were calculated to be β1 = 0.441, β2 = 0.469,β3 = 0.086 and β4=0.004.展开更多
With a special gauge transformation,the Lax pair of the derivative nonlinear Shcrdinger (DNLS) equation turns to depend on the squared parameter λ = k2instead of the usual spec-tral parameter k. By introducing a new ...With a special gauge transformation,the Lax pair of the derivative nonlinear Shcrdinger (DNLS) equation turns to depend on the squared parameter λ = k2instead of the usual spec-tral parameter k. By introducing a new direct product of Jost solu-tions,the complete Hamiltonian theory of the DNLS equation is constructed on the basis of the squared spectral parameter,which shows that the integrability completeness is still preserved. This result will be beneficial to the further study of the DNLS equation,such as the direct perturbation method.展开更多
The absorption and emission spectra of Nd3+:GdMgB5O10 crystal were inves- tigated. Based on Judd-Ofelt theory the three parameters of oscillator strength were obtained as follows: ?2 = 2.099×10-20 cm2, ?4 = 4.5...The absorption and emission spectra of Nd3+:GdMgB5O10 crystal were inves- tigated. Based on Judd-Ofelt theory the three parameters of oscillator strength were obtained as follows: ?2 = 2.099×10-20 cm2, ?4 = 4.599×10-20 cm2 and ?6 = 5.139×10-20 cm2. The fluorescence branch rations were also obtained: β1 = 0.424, β2 = 0.474, β3 = 0.094 and β4 = 0.005. The radiative lifetime is 416 μs and quantum efficiency ηc 9.13%. The emission cross section σp (1.06 μm) is 4.38×10-19 cm2.展开更多
The spectral parameters of Nd3+ ions in Nd3+:Klu(WO4)2 crystal were calculated based on Judd-Ofelt theory and obtained as follows: for the oscillator strengths ?λ: ?2 = 7.5029×10-20 cm2, ?4 = 7.1837×10-20...The spectral parameters of Nd3+ ions in Nd3+:Klu(WO4)2 crystal were calculated based on Judd-Ofelt theory and obtained as follows: for the oscillator strengths ?λ: ?2 = 7.5029×10-20 cm2, ?4 = 7.1837×10-20 cm2 and ?6 = 3.1189×10-20 cm2; the radiative lifetime is 123 μs; the quantum efficiency is equal to 64.55%; and β1 = 0.5498, β2 = 0.3943, β3 = 0.0551 and β4 = 0.0027 for the fluorescence branch ratios.展开更多
On the basis of the obtained intensity parameters Ω λ(λ =2,4,6) of Tm 3+ in the Na 5Tm(WO 4) 4 crystal, we performed calculations on the radiative transition probability, radiative lifetime, branching ...On the basis of the obtained intensity parameters Ω λ(λ =2,4,6) of Tm 3+ in the Na 5Tm(WO 4) 4 crystal, we performed calculations on the radiative transition probability, radiative lifetime, branching ratios and stimulated emission integrated cross sections between the two excited J manifolds of Tm 3+ , and discussed potentiality for the usage of this crystal as a laser material.展开更多
Significant wave period is an important parameter in coastal and offshore engineering design.Traditional spectral wave models do not directly calculate this parameter,which means that it needs to be estimated from the...Significant wave period is an important parameter in coastal and offshore engineering design.Traditional spectral wave models do not directly calculate this parameter,which means that it needs to be estimated from the spectral periods using empirical formulas.The wave energy period is one of the wave periods directly output by many wave models and is often used in studies of wave energy.This study investigated the relationship between significant wave period and wave energy period using wave data measured at three stations in the coastal waters of China.The observations recorded at these stations in the South China Sea,the East China Sea,and the Bohai Sea covered a wide range of surface wave conditions.Analysis indicated that the ratio of significant wave period to wave energy period is closely related to the Goda peakedness parameter of the wave spectra.Therefore,we proposed an empirical formula in which significant wave period is a function of wave energy period and the Goda peakedness parameter.Evaluation results showed that the performance of this formula is substantially better than that of fitting formulas that use constant coefficients.展开更多
While heavy rainfall frequently takes place in southern China during summer monsoon seasons,quantitative precipitation forecast skills are relatively poor.Therefore,detailed knowledge about the raindrop size distribut...While heavy rainfall frequently takes place in southern China during summer monsoon seasons,quantitative precipitation forecast skills are relatively poor.Therefore,detailed knowledge about the raindrop size distribution(DSD)is useful in improving the quantitative precipitation estimation and forecast.Based on the data during 2018-2022 from 86stations in a ground-based optical disdrometer measurement network,the characteristics of the DSD in Guangdong province are investigated in terms of the particle size distribution(N(D)),mass-weighted mean diameter(Dm) and other integral DSD parameters such as radar reflectivity(Z),rainfall rate(R) and liquid water content(LWC).In addition,the effects of geographical locations,weather systems(tropical cyclones,frontal systems and the summer monsoon) and precipitation types on DSD characteristics are also considered.The results are shown as follows.1) Convective precipitation has a broader N(D) and larger mean particle diameter than the stratiform precipitation,and the DSD observations in Guangdong are consistent with the three-parameter gamma distribution.The relationships between the Z and R for stratiform and convective precipitation are also derived for the province,i.e.,Z=332.34 R1.32and Z=366.26R1.42which is distinctly different from that of the Next-generation Weather Radar(NEXRAD) Z-R relationship in United States.2) In the rainy season(April-September),the Dm, R and LWC are larger than those in the dry season(OctoberMarch).Moreover the above parameters are larger,especially in mid-May,which is the onset of the South China Sea summer monsoon.3) The spatial analysis of DSD shows that the coastal station observations indicate a smaller Dmand a larger normalized intercept parameter(log10Nw),suggestive of maritime-like rainfall.Dmis larger and log10Nwis smaller in the inland area,suggestive of continental-like rainfall.4) Affected by such weather systems as the tropical cyclone,frontal system and summer monsoon,the DSD shows characteristics with distinct differences.Furthermore,frontal system rainfall tends to present a continental-like rainfall,tropical cyclone rainfall tends to have a maritime-like rainfall,and summer monsoon rainfall characteristic are between maritime-and continental-like cluster(raindrop concentration and diameter are higher than continental cluster and maritime cluster,respectively.)展开更多
This paper presented the studies on the optical properties and calculation of spectral parameters of europium doped lanthanum oxychloride nanophosphor for their possible applications in optoelectronic devices. The com...This paper presented the studies on the optical properties and calculation of spectral parameters of europium doped lanthanum oxychloride nanophosphor for their possible applications in optoelectronic devices. The compound was doped with 0.1 mol% Eu3＋ ions. The X-ray diffraction study of prepared sample suggested the tetragonal structure with particle size in the range of 18–21 nm. The photoluminescence （PL） emission spectra showed the bright emission in orange-red region from 580 to 630 nm. The most intense emission peak at 621 nm was due to transition 5D0→7F2 in energy levels of Eu3＋ ions. The spectral parameters were calculated from the absorption and emission spectra using Judd-Ofelt intensity parameters. The calculated values of the oscillator strength corresponding to the three transitions 7F1→5D1, 7F1→5D2 and 7F0→5D2 observed at 535, 472 and 465 nm in absorption spectra were 0.30×10–6, 1.36×10–6 and 0.63×10–6, respectively. The value of transi- tion probability （A）, stimulated emission cross-section （ ） and radiative lifetime （τrad） corresponding to 621 nm emission peak （transition 5D0→7F2） were 308 s–1, 1.22×10–21 cm2 and 3.24×10–3 s, respectively.展开更多
Pr（ Ⅲ ） and Nd（ Ⅲ ） can be utilized as absorption spectroscopic probes to investigate the interaction of biomolecules like Lysozyme （HEW） with Ca（ Ⅱ ） in-vitro ; the most abundant metal ion in the human bod...Pr（ Ⅲ ） and Nd（ Ⅲ ） can be utilized as absorption spectroscopic probes to investigate the interaction of biomolecules like Lysozyme （HEW） with Ca（ Ⅱ ） in-vitro ; the most abundant metal ion in the human body system. The spectroscopic techniques involving comparative absorption, absorption difference, and quantitative intensity analysis using 4f-4f transitions are utilized for changes in the inner sphere coordination pattern of Pr（ Ⅲ ） and Nd（Ⅲ ） in solution as well as in solid state. The present study deals with an important biomolecule in human metabolism, that is, Lysozyme （HEW）. The absorption er-Condon the probab spectral parameters such as the oscillator strength （P）, the Judd-Ofelt （Tλ） intensity parameters, and the Slatinter electronic parameters are calculated using chi square methods. The obtained results are used to determine le geometry of the complex in the solution, the nature of the bond between Pr（Ⅲ）/Nd（Ⅲ） with lysozyme, and the inner sphere coordination environment of f-f transitions. The results obtained from various experimental conditions are utilized to investigate the coordination changes in the Pr（Ⅲ）/Nd（Ⅲ） complexes caused by different coordinating sites of lysozyme, normalized bite, denticity, the solvent nature, the coordination number, the nature of bond and other parameters to mimic the interaction of the Ca（ Ⅱ ） ion with such biomolecule.展开更多
The polarized absorption spectra of Tm3+/Er3+:YVO4 crystal were measured at room temperature. Based on the Judd-Ofelt theory, the spectral parameters were obtained: the intensity parameters Wl of Tm3+ in Tm/Er:YVO4 cr...The polarized absorption spectra of Tm3+/Er3+:YVO4 crystal were measured at room temperature. Based on the Judd-Ofelt theory, the spectral parameters were obtained: the intensity parameters Wl of Tm3+ in Tm/Er:YVO4 crystal: W2 = 10.69×10-20, W4 = 0.604×10-20, W6 = 2.05×10-20 cm2 for the (100) face and W2 = 10.43×10-20, W4 = 0.13×10-20, W6 = 1.83×10-20 cm2 for the (001) face. Based on these values, the oscillator strength, radioactive lifetime and fluorescence branch ratio were calculated for Tm3+ in Tm/Er:YVO4 crystal.展开更多
This work studies the asymptotic formulas for the solutions of the Sturm-Liouville equation with the polynomial dependence in the spectral parameter. Using these asymptotic formulas it is proved some trace formulas fo...This work studies the asymptotic formulas for the solutions of the Sturm-Liouville equation with the polynomial dependence in the spectral parameter. Using these asymptotic formulas it is proved some trace formulas for the eigenvalues of a simple boundary problem generated in a finite interval by the considered Sturm-Liouville equation.展开更多
Frame erasure concealment is studied to solve the problem of rapid speech quality reduction due to the loss of speech parameters during speech transmission. A large hidden Markov model is applied to model the immittan...Frame erasure concealment is studied to solve the problem of rapid speech quality reduction due to the loss of speech parameters during speech transmission. A large hidden Markov model is applied to model the immittance spectral frequency （ISF） parameters in AMR-WB codec to optimally estimate the lost ISFs based on the minimum mean square error （MMSE） rule. The estimated ISFs are weighted with the ones of their previous neighbors to smooth the speech, resulting in the actual concealed ISF vectors. They are used instead of the lost ISFs in the speech synthesis on the receiver. Comparison is made between the speech concealed by this algorithm and by Annex I of G. 722. 2 specification, and simulation shows that the proposed concealment algorithm can lead to better performance in terms of frequency-weighted spectral distortion and signal-to-noise ratio compared to the baseline method, with an increase of 2.41 dB in signal-to-noise ratio （SNR） and a reduction of 0. 885 dB in frequency-weighted spectral distortion.展开更多
Municipal sewage from an oxidation ditch was treated for reuse by nanofiltration（NF） in this study. The NF performance was optimized, and its fouling characteristics after different operational durations（i.e., 48 a...Municipal sewage from an oxidation ditch was treated for reuse by nanofiltration（NF） in this study. The NF performance was optimized, and its fouling characteristics after different operational durations（i.e., 48 and 169 hr） were analyzed to investigate the applicability of nanofiltration for water reuse. The optimum performance was achieved when transmembrane pressure = 12 bar, p H = 4 and flow rate = 8 L/min using a GE membrane. The permeate water quality could satisfy the requirements of water reclamation for different uses and local standards for water reuse in Beijing. Flux decline in the fouling experiments could be divided into a rapid flux decline and a quasi-steady state. The boundary flux theory was used to predict the evolution of permeate flux. The expected operational duration based on the 169-hr experiment was 392.6 hr which is 175% longer than that of the 48-hr one. High molecular weight（MW） protein-like substances were suggested to be the dominant foulants after an extended period based on the MW distribution and the fluorescence characteristics. The analyses of infrared spectra and extracellular polymeric substances revealed that the roles of both humic- and polysaccharide-like substances were diminished, while that of protein-like substances were strengthened in the contribution of membrane fouling with time prolonged. Inorganic salts were found to have marginally influence on membrane fouling. Additionally, alkali washing was more efficient at removing organic foulants in the long term, and a combination of water flushing and alkali washing was appropriate for NF fouling control in municipal sewage treatment.展开更多
基金This work was supported by the National Natural Science Foundation of China (60378031) and Key Project of Science and Technology of Fujian Province (2001H1007)
文摘The spectral parameters of Nd^3＋ ions in Nd^3＋-doped NaGd（MoO4）2 crystal have been investigated based on Judd-Ofelt theory and obtained as follows： The intensity parameters Ωeff are Ω2 = 24.77×10^20, Ω4 = 7.31×10^-20 and Ω6 = 6.91×10^-20 cm^2. The radiative lifetime is 100 μs, and the quantum efficiency is 93.9%. The fluorescence branch ratios were calculated to be β1 = 0.441, β2 = 0.469,β3 = 0.086 and β4=0.004.
基金Supported by the National Natural Science Foundation of China (10705022)
文摘With a special gauge transformation,the Lax pair of the derivative nonlinear Shcrdinger (DNLS) equation turns to depend on the squared parameter λ = k2instead of the usual spec-tral parameter k. By introducing a new direct product of Jost solu-tions,the complete Hamiltonian theory of the DNLS equation is constructed on the basis of the squared spectral parameter,which shows that the integrability completeness is still preserved. This result will be beneficial to the further study of the DNLS equation,such as the direct perturbation method.
基金This work was supported by the National Natural Science Foundation of China (50272066) and Key Project of Science and Technology of Fujian Province (2001H107)
文摘The absorption and emission spectra of Nd3+:GdMgB5O10 crystal were inves- tigated. Based on Judd-Ofelt theory the three parameters of oscillator strength were obtained as follows: ?2 = 2.099×10-20 cm2, ?4 = 4.599×10-20 cm2 and ?6 = 5.139×10-20 cm2. The fluorescence branch rations were also obtained: β1 = 0.424, β2 = 0.474, β3 = 0.094 and β4 = 0.005. The radiative lifetime is 416 μs and quantum efficiency ηc 9.13%. The emission cross section σp (1.06 μm) is 4.38×10-19 cm2.
基金This work was supported by the National Natural Science Foundation of China (50272066) and Key Project of Science and Technology of Fujian Province (2001F004)
文摘The spectral parameters of Nd3+ ions in Nd3+:Klu(WO4)2 crystal were calculated based on Judd-Ofelt theory and obtained as follows: for the oscillator strengths ?λ: ?2 = 7.5029×10-20 cm2, ?4 = 7.1837×10-20 cm2 and ?6 = 3.1189×10-20 cm2; the radiative lifetime is 123 μs; the quantum efficiency is equal to 64.55%; and β1 = 0.5498, β2 = 0.3943, β3 = 0.0551 and β4 = 0.0027 for the fluorescence branch ratios.
文摘On the basis of the obtained intensity parameters Ω λ(λ =2,4,6) of Tm 3+ in the Na 5Tm(WO 4) 4 crystal, we performed calculations on the radiative transition probability, radiative lifetime, branching ratios and stimulated emission integrated cross sections between the two excited J manifolds of Tm 3+ , and discussed potentiality for the usage of this crystal as a laser material.
基金The National Natural Science Foundation of China under contract No.41821004the Basic Scientific Fund for National Public Research Institutes of China under contract No.2020Q08the Fund of Laoshan Laboratory under contract No.LSKJ202201600.
文摘Significant wave period is an important parameter in coastal and offshore engineering design.Traditional spectral wave models do not directly calculate this parameter,which means that it needs to be estimated from the spectral periods using empirical formulas.The wave energy period is one of the wave periods directly output by many wave models and is often used in studies of wave energy.This study investigated the relationship between significant wave period and wave energy period using wave data measured at three stations in the coastal waters of China.The observations recorded at these stations in the South China Sea,the East China Sea,and the Bohai Sea covered a wide range of surface wave conditions.Analysis indicated that the ratio of significant wave period to wave energy period is closely related to the Goda peakedness parameter of the wave spectra.Therefore,we proposed an empirical formula in which significant wave period is a function of wave energy period and the Goda peakedness parameter.Evaluation results showed that the performance of this formula is substantially better than that of fitting formulas that use constant coefficients.
基金National Natural Science Foundation of China(42075014,41975138)Natural Science Foundation of Guangdong Province(2022A1515011814,2021A1515011539,2020A1515010602)+3 种基金Open Grants of State Key Laboratory of Severe Weather(2022LASW-B15)Radar Application and Short-term Severe-weather Predictions and Warnings Technology Program(GRMCTD202002)Key Scientific and Technological Research Project of GRMC(GRMC2020Z03)Water Resource Science and Technology Innovation Program of Guangdong Province(2022-02)。
文摘While heavy rainfall frequently takes place in southern China during summer monsoon seasons,quantitative precipitation forecast skills are relatively poor.Therefore,detailed knowledge about the raindrop size distribution(DSD)is useful in improving the quantitative precipitation estimation and forecast.Based on the data during 2018-2022 from 86stations in a ground-based optical disdrometer measurement network,the characteristics of the DSD in Guangdong province are investigated in terms of the particle size distribution(N(D)),mass-weighted mean diameter(Dm) and other integral DSD parameters such as radar reflectivity(Z),rainfall rate(R) and liquid water content(LWC).In addition,the effects of geographical locations,weather systems(tropical cyclones,frontal systems and the summer monsoon) and precipitation types on DSD characteristics are also considered.The results are shown as follows.1) Convective precipitation has a broader N(D) and larger mean particle diameter than the stratiform precipitation,and the DSD observations in Guangdong are consistent with the three-parameter gamma distribution.The relationships between the Z and R for stratiform and convective precipitation are also derived for the province,i.e.,Z=332.34 R1.32and Z=366.26R1.42which is distinctly different from that of the Next-generation Weather Radar(NEXRAD) Z-R relationship in United States.2) In the rainy season(April-September),the Dm, R and LWC are larger than those in the dry season(OctoberMarch).Moreover the above parameters are larger,especially in mid-May,which is the onset of the South China Sea summer monsoon.3) The spatial analysis of DSD shows that the coastal station observations indicate a smaller Dmand a larger normalized intercept parameter(log10Nw),suggestive of maritime-like rainfall.Dmis larger and log10Nwis smaller in the inland area,suggestive of continental-like rainfall.4) Affected by such weather systems as the tropical cyclone,frontal system and summer monsoon,the DSD shows characteristics with distinct differences.Furthermore,frontal system rainfall tends to present a continental-like rainfall,tropical cyclone rainfall tends to have a maritime-like rainfall,and summer monsoon rainfall characteristic are between maritime-and continental-like cluster(raindrop concentration and diameter are higher than continental cluster and maritime cluster,respectively.)
文摘This paper presented the studies on the optical properties and calculation of spectral parameters of europium doped lanthanum oxychloride nanophosphor for their possible applications in optoelectronic devices. The compound was doped with 0.1 mol% Eu3＋ ions. The X-ray diffraction study of prepared sample suggested the tetragonal structure with particle size in the range of 18–21 nm. The photoluminescence （PL） emission spectra showed the bright emission in orange-red region from 580 to 630 nm. The most intense emission peak at 621 nm was due to transition 5D0→7F2 in energy levels of Eu3＋ ions. The spectral parameters were calculated from the absorption and emission spectra using Judd-Ofelt intensity parameters. The calculated values of the oscillator strength corresponding to the three transitions 7F1→5D1, 7F1→5D2 and 7F0→5D2 observed at 535, 472 and 465 nm in absorption spectra were 0.30×10–6, 1.36×10–6 and 0.63×10–6, respectively. The value of transi- tion probability （A）, stimulated emission cross-section （ ） and radiative lifetime （τrad） corresponding to 621 nm emission peak （transition 5D0→7F2） were 308 s–1, 1.22×10–21 cm2 and 3.24×10–3 s, respectively.
文摘Pr（ Ⅲ ） and Nd（ Ⅲ ） can be utilized as absorption spectroscopic probes to investigate the interaction of biomolecules like Lysozyme （HEW） with Ca（ Ⅱ ） in-vitro ; the most abundant metal ion in the human body system. The spectroscopic techniques involving comparative absorption, absorption difference, and quantitative intensity analysis using 4f-4f transitions are utilized for changes in the inner sphere coordination pattern of Pr（ Ⅲ ） and Nd（Ⅲ ） in solution as well as in solid state. The present study deals with an important biomolecule in human metabolism, that is, Lysozyme （HEW）. The absorption er-Condon the probab spectral parameters such as the oscillator strength （P）, the Judd-Ofelt （Tλ） intensity parameters, and the Slatinter electronic parameters are calculated using chi square methods. The obtained results are used to determine le geometry of the complex in the solution, the nature of the bond between Pr（Ⅲ）/Nd（Ⅲ） with lysozyme, and the inner sphere coordination environment of f-f transitions. The results obtained from various experimental conditions are utilized to investigate the coordination changes in the Pr（Ⅲ）/Nd（Ⅲ） complexes caused by different coordinating sites of lysozyme, normalized bite, denticity, the solvent nature, the coordination number, the nature of bond and other parameters to mimic the interaction of the Ca（ Ⅱ ） ion with such biomolecule.
文摘The polarized absorption spectra of Tm3+/Er3+:YVO4 crystal were measured at room temperature. Based on the Judd-Ofelt theory, the spectral parameters were obtained: the intensity parameters Wl of Tm3+ in Tm/Er:YVO4 crystal: W2 = 10.69×10-20, W4 = 0.604×10-20, W6 = 2.05×10-20 cm2 for the (100) face and W2 = 10.43×10-20, W4 = 0.13×10-20, W6 = 1.83×10-20 cm2 for the (001) face. Based on these values, the oscillator strength, radioactive lifetime and fluorescence branch ratio were calculated for Tm3+ in Tm/Er:YVO4 crystal.
文摘This work studies the asymptotic formulas for the solutions of the Sturm-Liouville equation with the polynomial dependence in the spectral parameter. Using these asymptotic formulas it is proved some trace formulas for the eigenvalues of a simple boundary problem generated in a finite interval by the considered Sturm-Liouville equation.
基金The Science Foundation of Southeast University(No.XJ0704268)the Natural Science Foundation of the Education Department of Anhui Province(No.KJ2007B088)
文摘Frame erasure concealment is studied to solve the problem of rapid speech quality reduction due to the loss of speech parameters during speech transmission. A large hidden Markov model is applied to model the immittance spectral frequency （ISF） parameters in AMR-WB codec to optimally estimate the lost ISFs based on the minimum mean square error （MMSE） rule. The estimated ISFs are weighted with the ones of their previous neighbors to smooth the speech, resulting in the actual concealed ISF vectors. They are used instead of the lost ISFs in the speech synthesis on the receiver. Comparison is made between the speech concealed by this algorithm and by Annex I of G. 722. 2 specification, and simulation shows that the proposed concealment algorithm can lead to better performance in terms of frequency-weighted spectral distortion and signal-to-noise ratio compared to the baseline method, with an increase of 2.41 dB in signal-to-noise ratio （SNR） and a reduction of 0. 885 dB in frequency-weighted spectral distortion.
基金supported by the Major Science & Technology Projects for Water Pollution Control and Management of China (Nos. 2012ZX07203-002 2015ZX07203-005)
文摘Municipal sewage from an oxidation ditch was treated for reuse by nanofiltration（NF） in this study. The NF performance was optimized, and its fouling characteristics after different operational durations（i.e., 48 and 169 hr） were analyzed to investigate the applicability of nanofiltration for water reuse. The optimum performance was achieved when transmembrane pressure = 12 bar, p H = 4 and flow rate = 8 L/min using a GE membrane. The permeate water quality could satisfy the requirements of water reclamation for different uses and local standards for water reuse in Beijing. Flux decline in the fouling experiments could be divided into a rapid flux decline and a quasi-steady state. The boundary flux theory was used to predict the evolution of permeate flux. The expected operational duration based on the 169-hr experiment was 392.6 hr which is 175% longer than that of the 48-hr one. High molecular weight（MW） protein-like substances were suggested to be the dominant foulants after an extended period based on the MW distribution and the fluorescence characteristics. The analyses of infrared spectra and extracellular polymeric substances revealed that the roles of both humic- and polysaccharide-like substances were diminished, while that of protein-like substances were strengthened in the contribution of membrane fouling with time prolonged. Inorganic salts were found to have marginally influence on membrane fouling. Additionally, alkali washing was more efficient at removing organic foulants in the long term, and a combination of water flushing and alkali washing was appropriate for NF fouling control in municipal sewage treatment.
